Ceballos Rodríguez-Conde, Fátima; (2025) A Comparative Evaluation of Bacterial Monocultures and a Synthetic Consortia for Plastic Degradation. Doctoral thesis (Ph.D), UCL (University College London).

Text Ceballos Rodriguez-Conde_Thesis.pdf - Submitted Version Access restricted to UCL open access staff until 1 April 2026. Download (108MB)

Abstract

Microbial systems offer a more sustainable and scalable approach to plastic degradation than chemical and enzyme-based strategies. While biofilm-forming bacteria show promise in addressing plastic pollution, their degradation rates are often variable and low. Microbial communities achieve more efficient resource utilisation through metabolic collaboration and division of labour than standard monocultures. This thesis adopts a novel bottom-up approach to design, test, and characterise microbial systems for degrading recalcitrant plastics. It identifies potentially relevant bacterial species and evaluates their effectiveness in plastic degradation, assessing whether bringing them together as a community enhances this process. Species were selected based on their ability to degrade polyethylene (PE) and/or polystyrene (PS), form biofilms, exhibit complementary growth, and biosafety level one status. Before testing the effectiveness of these selected species, PE and PS samples were subjected to pre-treatment strategies to evaluate chemical changes enhancing degradability, with UV light exposure identified as the most effective oxidation inducer. Additionally, a community profiling method was developed to assess community composition. Various analytical techniques characterised microbial action on the plastic substrate, revealing that direct weight loss measurement alone is insufficient for evaluating microbial degradation. Some strains formed robust biofilms on the plastic surface, introducing chemical modifications consistent with partial oxidation and degradation of the plastic. However, the synthetic community did not outperform individual strains in biofilm formation and chemical alteration of plastics. These results highlight that a systematic search can identify successful candidates for plastic breakdown. They also emphasise the complexity of microbial interactions and the need for further characterisation of complementary metabolism among community members to optimise the benefits of synthetic communities for plastic degradation. The findings underscore the necessity of evaluation methods beyond weight loss measurements to accurately assess microbial degradation. The developed framework provides a valuable foundation for evaluating microbial systems for plastic pollution mitigation.

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